02002nas a2200205 4500008004100000022001400041245010600055210006900161260000900230300001200239490000700251520129400258100002101552700001601573700002001589700002001609700001801629700002401647856012501671 2019 eng d a0740-322400aFiber optic Fabry-Perot interferometer sensor: an efficient and fast approach for ammonia gas sensing0 aFiber optic FabryPerot interferometer sensor an efficient and fa cMAR  a684-6890 v363 a

In this work, we propose and demonstrate a Fabry-Perot-interferometer-based polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA)-composite-coated optical sensor for ammonia and volatile organic compounds (VOCs) detection at room temperature. The principle of sensing is based on change in the cavity length of the FP cavity in the presence of varied concentrations of gases, which results in changes in the total reflectance due to the shift in wavelength of an interference pattern. The sensing composite material was coated on a single-mode optical fiber by using a simple dip-coating technique and explored it for sensing. The ammonia and VOCs measurements were performed for concentrations ranging from 5 to 500 ppm. The corresponding sensitivity and limit of detection of the developed sensor for ammonia gas detection was observed of the order of around 4.16 pm/ppm and 4.8 ppm, respectively. The response and recovery times of the sensor were found to be of the order of 50 s and 10 s, respectively, for the ammonia gas. This sensor provides a simple, cost-effective, highly sensitive, and repeatable approach to measure ammonia gas and other VOCs at room temperature and could fulfill the demands of industrial applications. (C) 2019 Optical Society of America

1 aKanawade, Rajesh1 aKumar, Ajay1 aPawar, Dnyandeo1 aLate, Dattatray1 aMondal, Samir1 aSinha, Ravindra, K. uhttps://library.ncl.res.in/content/fiber-optic-fabry-perot-interferometer-sensor-efficient-and-fast-approach-ammonia-gas02231nas a2200229 4500008004100000022001400041245009600055210006900151260000900220300001400229490000700243520146300250100002201713700001601735700002001751700002101771700002001792700002001812700002401832700001801856856012701874 2019 eng d a1094-408700aNegative axicon tip-based fiber optic interferometer cavity sensor for volatile gas sensing0 aNegative axicon tipbased fiber optic interferometer cavity senso cMAR  a7277-72900 v273 a

In this research work we demonstrated negative axicon optical fiber tip filled with Polydimethylsiloxane (PDMS) as a sensor platform for volatile organic gases detection at room temperature. The response of the sensor was measured with various Volatile Organic Compounds (VOCs) such as Chloroform, Hexane, Isopropanol, Acetone, Toluene and Methanol in the concentration ranging from 5 to 200 ppm. The corresponding sensitivity and limit of detection (LOD) of the developed sensor for the measured VOCs were observed between the order of around 23.7 to 3.2 pm/ppm and 0.84 to 6.10 ppm, respectively. The response and recovery time of sensor were found between the order of 30 to 57 seconds and 8 to 25 seconds respectively for the measured VOCs. Thermal stability of the developed sensor was also studied at 30-70 degrees C with intervals of 10 degrees C. The principle of sensing is based on change in the length of the Fabry-Perot Interferometric (FPI) cavity in the presence of varied concentrations of VOCs, which results in changes in the shift in wavelength of an interference pattern attributed to the change in PDMS filling the cavity length (swelling). The experimentally observed trends in the relative swelling of PDMS with VOCs are found in agreement with the theoretically calculated values obtained from the Hansen solubility parameter (HSP). The developed gas sensor has the potential to fulfill the demands of industrial applications.

1 aKanavvade, Rajesh1 aKumar, Ajay1 aPawar, Dnyandeo1 aVairagi, Kaushal1 aLate, Dattatray1 aSarkar, Sudipta1 aSinha, Ravindra, K.1 aMondal, Samir uhttps://library.ncl.res.in/content/negative-axicon-tip-based-fiber-optic-interferometer-cavity-sensor-volatile-gas-sensing02861nas a2200241 4500008004100000022001400041245016700055210006900222260000900291300001100300490000700311520196300318653002402281653003702305653001402342653004102356653001902397100001602416700002302432700002002455700002102475856012302496 2024 eng d a0091-328600aFabrication and evaluation of a spatially resolved fiber-optic probe for diffuse reflectance measurement for noninvasive diabetic foot ulcer diagnosis perspective0 aFabrication and evaluation of a spatially resolved fiberoptic pr cAPR  a0441030 v633 a

Timely diagnosis and monitoring of wound progression or healing are key to improving the long-term outcome of diabetic foot ulcers (DFU). Diffuse reflectance spectroscopy (DRS) has the potential to noninvasively diagnose the DFU in real time, as it detects changes in local blood volume fraction and oxygenation state level that occur when tissue becomes diseased or ulcerated. Since foot soles have a thicker epidermis and deeper blood vessels/capillaries than other parts of the body, a spatially resolved fiber-optic probe (SRFP) is needed to detect the optimal spatially resolved diffuse reflectance (SRDR) signal from the local site of the ulcer for DFU diagnosis. Therefore, herein, an SRFP consisting of a linear array of seven 400-mu m fibers with detector-source (D-S) fiber separation (rho) ranging from 0.8 to 4.8 mm was designed, fabricated, tested, and evaluated for SRDR measurement from a standard reflectance plate of barium sulfate (BaSO4) and foot sole of 27 healthy human subjects. The variation in SRDR spectra for each detector and source fiber pair measured with BaSO4 was found to be less than 1.6%. In-vivo measurements from the foot sole demonstrate that the fabricated probe has the ability to spatially resolve and distinguish the SRDR spectra from sites, namely, the fifth metatarsal, ball of great joint, calcaneum, and great toe. Experimentally and theoretically, the detector and source fiber pair of rho=1.6 and 2.4 mm were optimal for SRDR measurements from a human foot. To evaluate and validate the performance of SRFP in a context relevant to DFU diagnosis, further SRDS measurements were performed on the solid tissue phantoms that mimic the optical properties of the normal and diabetic foot sole, and their results are statistically found different. Preliminary results suggest that developed SRFP can be explored for DRS measurement from foot ulcer patients to confirm its potential clinical applicability.

10adiabetic foot ulcer10adiffuse reflectance spectroscopy10afoot sole10aspatially resolved fiber-optic probe10atissue phantom1 aKumar, Ajay1 aHattale, Gangadhar1 aPawar, Dnyandeo1 aKanawade, Rajesh uhttps://library.ncl.res.in/content/fabrication-and-evaluation-spatially-resolved-fiber-optic-probe-diffuse-reflectance02461nas a2200409 4500008004100000022001400041245008800055210006900143260000900212300001600221490000700237520122100244653001601465653002501481653001701506653001501523653002601538653001901564653002201583653001301605653002101618653001601639653004201655653001201697653001301709653002401722100002001746700002401766700002201790700002001812700001601832700002101848700002201869700002101891700002101912856011801933 2024 eng d a1530-437X00aPolymeric PEI/PEG coated optical fiber fabry-perot interferometer for CO2 detection0 aPolymeric PEIPEG coated optical fiber fabryperot interferometer  cDEC  a40883-408890 v243 a

Monitoring carbon dioxide (CO2) gas is essential for numerous applications, but the detection of CO2 in miniaturized devices presents significant challenges. In this study, a polyethyleneimine/poly(ethylene glycol) (PEI/PEG) coated optical fiber Fabry-Perot interferometer (FPI) and its charge transfer process toward CO2 are investigated. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to analyze the surface morphology and vibration bands of the PEI/PEG composite. The PEI/PEG composite Fabry-Perot (FP) cavity of length similar to 13 mu m is coated at the distal end of the single-mode fiber using a dip coating technique. A highly sensitive optical and low-cost FPI probe fabrication has displayed a linear sensitivity of 17.10 nm/% in the range of 0.31%-1.25% CO2 gas. The response and recovery times of the sensor are in a few tens of seconds. The enhanced performance of the sensor is primarily due to the protonation and charge transfer between CO2 gas molecules and PEI/PEG composite. Due to low-cost fabrication and high sensitivity, this FPI sensor can be used in a range of potential applications in bioprocessing, healthcare, and environmental monitoring.

10adip coating10aFresnel's reflection10aInterference10amonitoring10aOptical fiber sensors10aOptical fibers10apolymer composite10aPolymers10arefractive index10asensitivity10aSensor phenomena and characterization10asensors10aswelling10aTemperature sensors1 aPawar, Dnyandeo1 aPresti, Daniela, Lo1 aLemma, Enrico, D.1 aRainer, Alberto1 aKumar, Ajay1 aKanawade, Rajesh1 aSilvestri, Sergio1 aSchena, Emiliano1 aMassaroni, Carlo uhttps://library.ncl.res.in/content/polymeric-peipeg-coated-optical-fiber-fabry-perot-interferometer-co2-detection02882nas a2200289 4500008004100000022001400041245015800055210006900213260000800282300001100290490000800301520188200309653002402191653003702215653001802252653002202270653001802292653002302310100001602333700001902349700002002368700002102388700001702409700001902426700002102445856012602466 2025 eng d a0030-399200aReal-time estimation of blood oxygenation parameters from human foot sole during leg elevation: a preliminary study with diffuse reflectance spectroscopy0 aRealtime estimation of blood oxygenation parameters from human f cFEB a1117060 v1813 a

This study investigated the applicability of diffuse reflectance spectroscopy (DRS) for real-time and non-invasive measurement of blood oxygenation parameters (BOPs) such as reduced hemoglobin (RHb), oxyhemoglobin (HbO(2)), and oxygen saturation (SO2) from human foot sole during leg elevation. Seventeen (17) healthy male subjects aged between 21 to 39 years were included in this study. Diffuse reflectance spectra were recorded from measurement sites namely the 5th metatarsal, ball of great joint, calcaneum, and great toe of the human foot sole w.r.t. leg elevation angles such as 0(0), 15(0), 30(0), 45(0), and 60(0), respectively. The localized BOPs were derived from the recorded spectra. In addition, blood hemodynamic parameters (BHPs) such as heart rate (HR), SO2, perfusion index (PI), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were also measured for each elevating angle. To study and assess the changes in BOPs and BHPs w.r.t. leg elevation, a One-way ANOVA test followed by a Tukey HSD post-hoc test was performed. We observed a statistically significant increase in RHb (p < 0.001) and a decrease in HbO(2) (p < 0.001) after 45 degrees of leg elevation, however, there was no statistically significant difference in SO2 (p = 0.74) and HR (p = 0.84) for each measurement site w.r.t. leg elevation, respectively. Furthermore, PI (p < 0.01), ankle SBP (p < 0.001) and DBP (p < 0.001) were decreased w.r.t. leg elevation. The obtained results are in agreement with the literature. The preliminary results suggest that DRS has the potential for real-time estimation of BOPs from the local sites of healthy human foot soles during leg elevation. Thus, it opens the possibility of DRS to monitor and evaluate the diagnosis and treatment of ischemia and edema during leg elevation of patients through BOPs measurement.

10adiabetic foot ulcer10adiffuse reflectance spectroscopy10aLeg elevation10aOxygen saturation10aOxyhemoglobin10aReduced hemoglobin1 aKumar, Ajay1 aLohchab, Viney1 aPawar, Dnyandeo1 aSomeshwar, Vimal1 aMathe, Vikas1 aHusale, Sudhir1 aKanawade, Rajesh uhttps://library.ncl.res.in/content/real-time-estimation-blood-oxygenation-parameters-human-foot-sole-during-leg-elevation